Impact of biofilm on the ship propulsion characteristics and the speed reduction

Ship fuel consumption and the greenhouse gas emissions in the service are affected by various factors, including waves, wind, biofouling, corrosion, confined water. One of the operational measures for the reduction of the fuel consumption is the optimization of the maintenance schedule, but lack of information related to the potential benefits of the application of this measure represents an important barrier. Therefore, the prediction of the impact of biofouling on ship hydrodynamic characteristics is important. In this paper, a numerical model based on Reynolds Averaged Navier-Stokes (RANS) equations, which allows the prediction of the impact of biofilm on the ship propulsion characteristics is proposed. Roughness function models representing surface conditions of biofilm fouling were employed within the wall function of the CFD software. Thereafter, a detail analysis of the impact of biofilm on the propulsion characteristics and the flow around full-scale containership is presented. This study has demonstrated that the occurrence of biofilm should not be ignored and that the presence of biofilm can cause extremely detrimental effects on ship hydrodynamic characteristics. Thus, it is shown that the biofilm can cause a significant increase in delivered power and consequently an increase in fuel consumption or a decrease in ship speed, contradicting the often ignoring of the biofilm presence on the ship hull